Musical instruments, particularly organs, may comprise large numbers of so-called magnets, usually specially adapted electromagnets. Pipe organs are often fitted with pipe action-magnets, electromagnetic valves that control the admission of air into pipes, usually one magnet per pipe. Pipe organs are also often equipped with stop action-magnets, called SAM's, which are manually or electromagnetically operated switches used to select ranks of organ pipes. Musical instruments comprising no pipes may be fitted with SAM's to select ranks of sounds. U.S. Pat. No. 4,851,800 teaches pipe action-magnets and both tab-style and draw-knob SAM's, all typically used in pipe organs.
Pipe action-magnets are usually addressed and driven by circuitry located on driver cards, each card often servicing thirty-two or sixty-four pipes. Each pipe action-magnet usually has two coil terminals, one often connected in common with other pipe action-magnet terminals, and the other connected to an output of a driver card. A traditional pipe organ rank often comprises sixty-one pipes installed upon a wind chest having dimensions of several feet, with a driver card to service the pipes often located several feet away. If an average distance of ten feet from pipe to card be assumed, six-hundred-ten feet of wire is needed for the individual connections from card to pipes, not including common wiring. Since a pipe organ may comprise several tens of ranks totaling thousands of pipes, the wiring needed is often difficult and costly to install and maintain. U.S. Pat. No. 4,341,145 provides a pipe action-magnet comprising an electronic switch, allowing common connection of wires carrying large currents to pipe magnets and, permitting thinner wires to to control pipe action-magnets. This improvement reduces the wire cost and bulk, but not complexity, of pipe organ action-magnet wiring.
An organ is often fitted with one to three hundred stop action-magnets, or SAM's. Most SAM's comprise two coils, one to turn on a rank of sound, and another to turn it off, both usually addressed and driven by a driver card as with pipe action-magnets. To control ranks of sounds, each SAM additionally comprises one or more switches to which other parts of the musical instrument respond. These switches are usually wired to input cards that detect, and transmit to other parts of the organ, SAM position. Each input card may service perhaps sixty-four SAM switches. Thus, a SAM typically requires approximately thrice the individual, non-common, wiring, and thrice the card circuitry, of a pipe magnet. A theatre pipe-organ known to this inventor comprises about two-hundred-seventy SAM's, requiring a wiring harness, from a bolster upon which the SAM's are mounted to corresponding the driver cards mounted in the organ console, some six feet long and several inches in diameter and containing about eight-hundred wires.
To reduce SAM wiring, the Opus-Two SC Module is offered by Essential Technology of Kanata, Ontario, Canada. Being interposed in data and power wiring paths, such a module incurs added electrical connections.
Power consumption and resultant heat, and stray magnetic fields have hitherto militated against integration of either drive or decoder circuits into SAM's. Thus, a need remains for a musical instrument action-magnets and drivers that include drive and decoder, and signaling circuitry to provide simple, reliable, compact, and economical wiring and logic element reduction for control circuitry of musical instruments such as organs.